Alkylation process



Jan. 15, 1946. A J. ABRAMS ET A1.

ALKYLATION PROCESS Filed April 13, 1945 Patented Jan. l5, 1946 OFFICEALKYLTION PROCESS Armand J. Abrams and Carl S. Kuhn, Jr., Dallas.

Tex., assignors,

by mesne assignments, to

Socony-Vacuum Oil Company, Incorporated, New York, N. Y., a corporationof New York Application April 13,1945, Serial No. 588,214

17 Claims.

`'I'his invention relates to alkylation and relates more particularly tothe alkylation of isoparains Wifl olens in the presence of liquidhydrofiuoi'ic ac As is well/known, low boiling isoparans such asisobutane can be alkylated with low boiling olens such as the butenes inthe presence of liquid hydrofiuoric acid catalyst to produce saturatedbranched chain hydrocarbons having desirable octane number, leadsusceptibility, volatility characteristics, etc., making them highlyimportant as aviation fuel and high quality motor fuel. This alkylationreaction is commonly carried out by feeding the isoparafn and olefin toan alkylation reaction zone along with the hydrofluorio acid catalystwith which the hydrocarbons including the alkylate products areimmiscible and intimately contacting the acid phase with the hydrocarbonphase through formation of an emulsion. The reaction emulsion iswithdrawn from the alkylation reaction zone and sent to a separationzone wherein the acid phase and the hydrocarbon phase. are separated bygravity settling. The acid phase is recycled to the alkylation reactionzone, and the hydrocarbon phase is fractionated to separate the excessisoparailin reactant from the alkylate product for recycling.

Heretofore, it has been considered that the primary factors aiecting theyield and quality of the alkylate product were the ratio of isoparaiiinto olefin, the temperature of the reaction, and the concentration,expressed as titratable acidity, ofv

the hydrofiuoric acid catalyst. It has been recently discovered,however, that the reaction time, i. e., the total time during which thehydrocarbon reactants and alkylate products are in contact with thehydroiluoric acid catalyst, is an extremely important variable. Inisobutane alkylation, for example, as disclosed in the `copendingapplications, Serial No. 546,111, filed July 22,

1944, and Serial No. 565,794, filed November 29,

1944, the reaction time employed greatly affects the yield and qualityof the alkylate product and that, in certain instances as hereinafterindicated, maximum yields of highest quality products are obtained onlyby employing short reaction times, as, forexample, reaction times of buta few seconds. Thus, a'careful control of reaction time is essentialwhen short reaction times are required to obtain high yields of highquality products. While, with the usual types of commercial allqrlationreactors, a satisfactory control of the reaction time may be obtained inthereactor per se, a further reaction time is involved in the separationzone wherein the acid vand hydrocarbons may be in contact with eachother for a period of from about 30 seconds to 2 minutes,

depending upon the design of the separation zone' and the temperature ofoperation, before the emulsion completely separates. Accordingly, thetime required for separation of the acid catalyst from the hydrocarbonsimposes a limiting factor upon control of the reaction time andconsequently imposes a limiting factor upon the bene fits to be obtainedthereby.

It is an object of this invention to provide a new and improvedalkylation process. It is another object of this invention to provide amethod for controlling reaction time in alkylation reactions employinghydrouoric acid catalyst. It is another object of this invention toprovide a method for obtaining very short reaction times in hydrofluoricacid catalyzed alkylation reactions. It is another object of thisinvention toprovide a process for obtaining maximum yields of highestquality product from isoparafiin-olen alkylation reactions whereinhydrouoric acid is employed as the catalytic agent. Further objects andad,

from the following description thereof.

v In carrying out the invention, hydroiiuoricl acid andisoparailin-oleiin alkylation reactants are continuously passed to andwithdrawn from an alkylation reaction zone under conditions of ilow suchthat the acid and hydrocarbons are maintained in intimate contact for adesired predetermined period of time. After leaving the reaction zoneand after the acid and hydrocarbons have been in contact for the desiredpredetermined period of time, the hydroiiuoric acid catalyst containedinthe reaction mixture is diluted to a concentration with respect to waterbelow which the hydroiiuoric acid is ineiective as an alkylationcatalyst. For diluting the hydrouoric acid catalyst to below itseiective catalyst concentration, the reaction mixture may be admixedwith water, but, for reasons of economy, the reaction mixture ispreferably admixed with recycle dilute aqueous hydrofiuoric acidobtained in the manner hereinafter indicated. The reaction mixturecontaining the quenched acid is then separated into an aqueous acidphase and a hydrocarbon phase by conventional means and the hydrocarbonphase is subjected to conventional treatment for removal and recyclingof excess isoparamn reactant and recovery and purication of alkylateproduct. The aqueous hydroiluoric acid phase is subjected tofractionation to remove an overhead lhydroiluoric acid fraction ofcatalyst concentration which is recycled as catalyst to the alkylationreaction zone and to removea bottoms iraction of dilute aqueous hydrofluoric acid below catalyst concentration which is recycled fordilution of the catalyst acid in the reaction mixture to stop urthercatalytic action.

The essential element of 'the process o f the invention resides in thedilution of the hydroiluoric acid catalyst contained in the reactionmixture to a concentration with respect to water below the effectivecatalyst concentration at the end of the desired predetermined reactiontime. By thus diluting the catalyst, the alkylation reaction'may- 4 withpositive control of reaction time is provided.

' The extent to which the acid catalyst contained in the reactionmixture must be diluted to stop its catalytic activity isa function ofthe temperature of the reaction mixture and, to some extent, the amountof hydrocarbons and hydrocarbon polymers dissolved in the catalyst. Athigher temperatures, a greater dilution ofthe catalyst is required toquench its activity `than at lower temperatures. Thus, for example, attemperatures of C., dilution of the catalyst to a concentration belowabout 90% by weight has been found to stop effectively its activity,while at higher temperatures dilution to a lower concentration will berequired. Generally, for temperatures up to about 50 C., the reactionmay be stopped by dilution to a concentration bei ow about '75% byweight of hydrouoric acid. I Jwever, as

before mentioned, the amount of hydrocarbons and hydrocarbon polymers.dissolved in thecatalyst also aiiects the concentration to which thecatalyst must be diluted to stop its activity, and the concentrationsmentioned above will vary to a greater or lesser extent in anyparticular case depending upon the amounts of dissolved hydrocarbons andpolymers. From the standpoint of economy of operation, it is desirable'to dilute the exchange between the oleiin and the isoparamn and betweenthe oleiln polymer and the isoparafiln, alkylation of the isoparafiinwith products of the hydrogen exchange reactionaetc. Generally, inalkylation reactions wherein branched-chain olens or oleflns having thedouble bond in a non-terminal position are employed, the primaryalkylate products are the more desirable 'products, while, in alkylationreactions wherein olefins, except propylene, having the double bond in aterminal position, are employed, certain of the secondary products andproducts of the side reactions are the more desirableproducts. Proplyenebehaves like the branched chain and nonacid catalyst to a concentrationno lower than is necessary to quench its catalytic activity sincethereby the amount of quenched acid to be fractionated into recyclecatalyst and quenching acid is kept at a minimum, and the amount ofquench-v ing acid to be recycled is minimized.

It will be understood that hereinabove as well as hereinafter, unlessotherwise speciiied, by weight vper cent of hydrouoric acid is meant theactual weight per cent of hydrouoric acid in the acid-water mixtures andnot the weight per cent of acid expressed as titratable acidity sincethe titratable acidity varies with the amount of dissolved hydrocarbonsand "hydrocarbon polymer contained in the acid-water mixtures,irrespective ofv the actual hydrofluoric acid concentration, and is nota true measure oi the actual hydronuoric acid concentration;Y

Isoparaiiin-olen alkylation is a complex reaction apparently involvingfirst the formation of primary alkylate products by condensation of theisoparafdn with the olefin followed by secondary reactions catalyzed bythe hydrofiuoric acid and involving isomerization and disproportionationof theprimary alkylate products to produce secondary alkylate products.Side reactions also occur terminal double bond oleilns in that generallythe primary alkylate product is more desirable than its isomers having astraight chain containing the same number of carbon atoms from thestandpoint of octane rating. The various reactions take place atdifferent rates and the temperature of reaction affects each of theserates. Thus, for

each type of olefin and for each temperature ol reaction, properselection of the reaction time must be made in order to obtain thedesired products in maximum amounts possible whether the primaryproducts or the secondary and side reaction products are desired,` asthe case may be.

In isobutane-propylene alkylation, the' primary alkylate product,2,3-dimethylpentane, is a more desirable product than the principalsecondary reaction product, 2,4-dimethylpentane, produced for example by-isomerization of the primary alkylate product. The primary alkylationreaction takes place rapidly as compared with the secondaryisomerization reaction, and a reaction time may, therefore, be selectedto permit the primary reaction to go substantially to completionbeforethe secondary reaction has gone to such an extent as to form sulcientquantities of the undesirable secondary reaction product to decrease theaverage quality of the alkylate product obtainedl The following tablegives the preferred range of reaction times for various Table ITemperature, PC. Reaction time In isobutane-butene alkylation, theproduct desired depends upon the olefin employed.

f Where isobutene or butene-2 is the olefin employed, the primaryalkylate products, trimethylpentanes, are the'more desirable products,and the secondary isomerization reaction results in the formation ofless highly branched and therefore less desirable octanes, and thesecondary reaction of` disproportionation results in the formation ofless desirable heptanes, nonanes, etc. On the other hand, where butene-lis the olen employed, the primary alkyla'te products are of poor qualitycontaining considerable quantities lof dimethylhexanes, whereas thesecondary reaction of isomerization results in the formation involvingpolymerization of the olen, hydrogen of products or improved quality.However, the

` 2,392,982 other secondary reaction, disproportionation. asl

in the case of isobutene and butene-2, results in the formation ofproducts of poor quality. Thus, where isobutene or butene-2 is employed,the reaction time is selectedto permit the primary reaction to go as faras possiblehtowards completion .before the secondary reactions ofisomerization and disproportionation have gone to a suiiicient exten-tto result in a decrease in the average quality of the product obtained.Where butene-l is employed, the reaction time is selected to permit thesecondary reaction of isomerization to go as far as possible towardscompletion before the secondary reaction of disproportionation has goneto an extent suiicient to decrease the average quality and yield of 'theproduct obtained.

In commercial isobutane-butene alkylation reactions, butane-butenemixtures, obtained for example by partial dehydrogenatioznv of butanefractions separated froml natural gas or straight,

run naphthas, fractionation of cracking still gases, etc., andcontaining butene-i, butene-2, and lsobutene in vary proportions, areordinarily employed as feed stock. When employing "these mixtures, thereaction timerequired to obtain the highest yields of the desiredproducts will depend upon the ratio o f the amount of butene-l containedin the mixtures to the amount of butene-2 plus isobutene, and for eachtemperature will lie between the time required for pure butenel and the.time required for pure butene-2 and isobutene. 'The following tablegives the preferred range of reaction times, as determined by the methoddisclosed in .the other of the aforementioned copending applications,Serial Number 565,794, for pure butene-Z or isobutene and for abutane-butene mixture containing by volume in the oleiinic portion ofthe mixture 51% butene-l. 14% butene2, and 35% isobutene.

Table II Reaction time Temperature, C.

Butene-butene mixtures Buteurs-2 or isobutene fected by passing thereaction mixture to a quenching vessel wherein the admixture may takeplace. Where the'quenchlng acid is admixed with the reaction mixture inthe outlet line of the alkylation reactor, turbulent fiow is preferablymaintained in order to obtain rapid and thorough admixture of quenching`acid and reaction mixture. Where a separate quenching apparatus isdesired, any suitable type of apparatus wherein rapid and thoroughadmixture can be obtained may be employed, as, for example, an enclosedvessel provided with means for agitating the reaction mixture andquenching acid, such as la circulating pump. stirrer, turbo-mixer, etc.

In carrying out the process of the invention, the velocity of flowthrough the reactor is regulated so that the acid and hydrocarbons arein .contact for the predetermined desired reaction time at the time ofadmixture with the aqueous quenching acid. This may be readilyaccomplished by control of the feed rate of acid and hydrocarbonreactants to the alkylation reactor taking into account the reactorvolume. Thus, for a given reactor volume including the volume of thereactor eilluent line to the point of effective quenching, the totalfeed rate of acid and hydrocarbon reactants for a desired reaction timemay be determined by dividing the reactor volume by the feed rateexpressed in volumes per unit time.

Following quenching of the catalyst, the mixture of quenched catalystand hydrocarbons is passed to'a separation zone, as, for example, agravity settler, for separation of the quenched acid from thehydrocarbons. The hydrocarbons any Asuitable type of reactor whereincontrol of be employed. However, where reaction times of less than aminute are indicated, a` single Vpass reactor is preferred.

Dilution of the acid catalyst in the reactionI mixture may be effectedby admixing. the aqueous -hydroiluoric acid with the reactionmixture inthe outlet line of the alkylation reactor or may be efare removed fromthe separation zone and may thereafter be treated in accordance withconventional procedures for removal of dissolved hydrofluorlc acid,removal and recycling of excess so isoparamn, recovery'of alkylateproduct, etc.

The quenched acid phase separated from the hydrocarbon phase in theseparation zone is subjected to fractionation for` separation of anoverhead fraction having a concentration of hydrouoric acid at leastsuiliciently high to be effective as catalyst, and a bottoms fractionhaving a concentration of hydrofluoric acid below the conto the amlationreactor eiiluent. The total amount of vquenched 'acid from theseparation zone may be thus subjected to fractionation. or the quenchedacid from the separation zone may be divided into two streams, ifdesired, and one stream subjected to fractionation as described.

The other stream may be admixed with the overhead fraction from thefractionation operation and recycled to the alkylation reactor, or maybe admixed with the bottoms fraction from the fractionation operationand recycled to the quenching operation, or the stream may be dividedinto two portions, one portion being admixed with the overhead fractionand the other portion being admixed with the bottoms fraction. Where thelatter procedures are employed, it will be understood, of coinse, thatthe proportion of quenched acid admixed with the overhead fraction andthe hydrouoric "acid concentration of both the overhead fraction and thequenched acid must be such that the hydrofiuoric acid concentration ofthe resultant mixture entering the al.- kylation reactor` is within theeffective catalyst concentration. The same considerations apply withrespect to the resultant mixture recycled to of either hydrofluoric acidor water alone.

made by those skilled in the art on the basis oi' material balances andeconomy oi' operation.

Hydroiluoric acid and water form a maximum boiling azectropic mixture,i. e., a mixture having a boiling point higher than the boiling point Atatmospheric pressure, this azeotropic mixture boils at about 120 C. andhas a composition of approximately 36 weight per cent hydrofluoric acid'and .64 weight per cent water. viously indicated, the quenched acidsubjected to fractionation will ordinarily have a hydroiluoric acidcontent of not below about 75 weight per cent and, since the hydrouoricacid boils at atmospheric pressure at about 19 C., as com- -pred with120 C. for the azeotropic mixture,

separation of substantially anhydrous hydrouoric acid as an overheadfraction and azeotropic mixture as a bottoms fraction may be readilyattained.

Fractionation of the quench'ed acid from the settler need not be carriedout, however, to provide an overhead fraction of substantially anhydrousacid and a bottoms fraction of azeotropic mixture, but the fractionationmay be carried out to obtain an overhead fraction of any desiredconcentration of hydrofluoric acid, provided the concentration is withinthe range of eil'ective catalyst concentration, or, where a portion ofthe quenched acid is recycled directly to the alkylation reactor afteradmixture with' the overhead fraction, sufficiently high to bring thehydroiluoric acid concentration of the mixture entering the alkylationreactor within theeflective catalyst range. Furthermore, thefractionation may be carried out to obtain a bottoms fraction of anydesired concentration of hydrofluoric acid above 36 weight per cent.Generally, where the total amount of quenched acid is subjected tofractionation, the

fractionation may be carried out to provide an' overhead fraction of 90to 100 weight per cent hydrofluoric acid and a bottoms fraction of 36 to65 weight per cent hydrofluoric acid; Where a portion of the quenchedacid is recycled directly to the alkylati'on reactor, the fractionationis prefdiluted, etc., and the selection of the concentrations of the twofractions can be readily made on Athe basis of these considerations bythose skilled in the art. After operations' have been set up for anygiven concentration in the two fractions, a

material balance will be maintained, and it will be only necessary toadd asmall amount of makeup-hydrouoric acid to the system to compensatefor lany loss that may be encountered. The addition of make-up waterwill seldom be necessary since generally enough will be picked upu fromwater in the hydrocarbon feed reactants to compensate for any losses.

-In order to Aprevent excessive rise in tempera- As preture of thereactor eIlluent upon admixture with the aqueous quenching acid as aresult of th'e'heat evolved by dilution of thehydroiiuoric acidcontained in the reactor elliuent, it is desirable to cool at leastaportion of. the quenching acid prior to admixture with the reactoreiliuent. Cooling may he carried out toany desired temperature above thefreezing point of the quenching acid which in the' case of theazeotropic mixture is about 16 C. Quenching acid having a concentrationof hydrotluoric acid, higher than that of the azeotropic mixture will,of course, have a. lower freezing point. Generally, cooling may becarried out just sumcientl'y to compensate for the rise in temperatureof the reactor eilluent upon dilution, and cooling to temperaturesbetween 16 C. and 0 C. is satisfactory depending upon the volume ofquenching acid employed per volume of -reactor eilluent, the proportionof the total amount of quenching acid cooled, and the rise intemperature of the reactor eilluent.

All apparatus coming in contact with the aqueous quenching acid and/orthe quenched acid catalyst, i. e., the quenching vessel when such isemployed, the quenched acid catalyst fractionation equipment, the tarsettler, the heat exchanger for cooling the recycle quenching acid,connecting pipe lines, valves, etc., should be constructed of materialsresistant to the corrosive action of dilute .hydroiluoric acid. Suitablematerials of construction for this apparatus include monei metal orother alloys such as the Hostelloys which contain a high percentage ofnickel. Apparatus coming in contact with the relatively concentratedcatalyst acid, such -as the alkylation reactor, may be constructed ofthe usual materials employed in the alkylation art, as, for example, lowcarbon steel or copper.-

In carrying out the alkylation reaction per se, any suitable reactionconditions with respect to isoparafhn-olefin ratio, acid-hydrocarbonratio, and titratable acidity of catalystmay be employed. Thus, forexample, where the process of the invention is applied to the alkylationof isobutane with' butenes, an isoparain-olenn volume ratio of about 2to 1 to l5 to 1,'an acid-hydro-.

carbon volume ratio of between about l to 2 and 2 to 1, orhigher, andhydroiiuoricacid havinga I titratable acidity of between about 82 percent Aand 100 per cent may be employed. The same.

reaction conditions may-be employed in the case of isobutane-propylenealkylation although it may be found desirable to employ hydrotluoricacid havinga titratable acidity higher than about 82 per cent.Similarly, in th'e case of other allavlation reactions, such as thealkylation of isopentane with propylene, butylene, etc., any suitablealkylating conditions may be employed.

The accompanying drawing is a flow sheet schematically illustrating onemethod of carrying out the process of theinvention inA connection 'withisobutane-butene alkylation.

Referring now tothe drawing, isobutane feed enters the system throughline I0 and is admixed with butene feed entering the system through line.I I. The combined'feeds are then admixed with recycle isobutane fromline I2 and recycle hydroiluoric acid from line I4 and passed. toalkylation reactor I5. To control the reaction time in the peraturecontrolling medium may be passed, although, as mentioned hereinbefore,any suitable type of alkylation reactor may be employed. The rates ofilow oi the streams of isobutane, butene, and hydrouoric acid beingcontrolled, the reaction mixture passes through the alkylation reactorat the desired rate and the effluent leaving the reactor through line 2lenters quencher 22 provided with stirrer 2B at the end of the desiredreaction time. The eilluent in the quencher 22 is admixed with cooleddilute aqueous quenching acid entering the quencher through line 25 andthe mixture is then passed through line 26 to settler 21 where themixture separates into an ipper hydrocarbon layer and a lower aqueousacid ayer.

The hydrocarbon layer is passed from settler 2i through line 29 to acidstripper 30 where any acid and water,- dissolved or suspended, isstripped from the hydrocarbons as overhead and returned aftercondensation in condenser 3l to the settler 27 through line 32 connectedwith line 26. The bottoms from stripper 3U are passed through line 3d todeis'obutanizer 35 for removal of isobutane.

Prior to entering the deisobutanizer, the bottoms from stripper 3@ maybe subjected to chemical treatment as by passing through a reactorpacked with bauxite (not shown) to remove residual tracesof hydrouoricacid and organic uorides. The isobutane is removed as overhead throughline 3S and after condensation in condenser 3lv passed to accmnulator 39from which it is recycled through line i2 to the alkylation reactor i5.Light gases are vented from the system through line to. The bottoms fromdeisbutanizer 35 are passed through line ft2 to debutanizer di wherenormal butane formed during the reaction or which may have beencontained in the feed hydrocarbons is removed as overhead through lined5. The debutanizer bottoms are passed through line i6 to fractionator.t7 where'the alkylate product is separated into aviation alhlate andheavy alkylate. The heavy alkylate is removed as bottoms through lineQ9, and the aviation alkylate is removed as overhead through line 50 andcondensed in condenserl.

The aqueous acid layer in settler 2l is removed through line v52 andpassed to hydrouoric acid fractionation column .'54 .where it isseparated into an overhead fraction containing lhydroiluoric acid insumcient concentration to be effective as catalyst and a bottomsfraction of aqueous quenching acid. The overhead catalyst fraction ispassed through line 55 to condenser 58 and after condensatlon passed toaccumulator 51 from which it is recycledthrough line iB to thealkylation reactor l5. Line y59 is connected with line M for theaddition of make up hydroiiuoric acid to the system to replace thatwhich may be lost or removed in the form of alkyl iiuorides. The bottomsfraction from the column 54 is passed through line St to tar settler 8|wherein any tar contained in the bottoms fraction is separated therefromand removed through line 62. 'I'he quenching acid is then passed throughline 25 containing line *36 'for the addition of any make up water whichmay be required and, after cooling in cooler 65, passed to the quencher22.

' Various modications maybe made in the above described procedures. Forexample, as hereinbefore indicated, the entire portion of quenched acidfrom the settler '21 need not be passed tothe fractionation column 5H,but a portion may be removed through line t6 from line 52 and partrecycled to the alkylationreactor through line 61 connected to line I4and the remainder recycled to the quencher through line 68 connected toline 25, or all may be recycled to the alkylation reactor or all may berecycled to the quencher. Additionally, only a. portion of the quenchingacid in line 25 need be cooled in cooler 85. the remainder being passedthrough by-pass line 10. Other modifications'will be readily apparent tothose skilled in the art.

Having thus described our invention, it will be understood that suchdescription has been given by way oi illustration and example only andnot by way of limitation, reference being had for the latter purpose tothe appended claims.

We claim:

1. A- process of controlling reaction time in a hydrofluoric acidcatalyzed isoparaln-oleiin alkylation reaction comprising diluting thehydroiiuoric acid catalyst contained in the alkylation reaction mixtureto a concentration below its effective catalyst concentration byadmixing water therewith at the end of a predetermined reaction time.

2. In an alkylation process wherein an isoparailln, an olen, andhydrofluoric acid catalyst are intimately contacted in an alkylationreaction zone, the improvement comprising diluting the hydrouoric acidcontained in the resulting reaction mixture to a Aconcentration belowits effective catalyst concentration by admixing water therewith at theend of a. predetermined reaction time whereby effective control of thetotal reaction time is obtained.

3. In a continuous alkylation process wherein an isoparaiin, an oleiin,and hydroluoric acid catalyst are maintained in intimate contact in analkylation reaction zone for a predetermined reaction time, reactionmixture of hydrocarbons and hydroiiuoric acid catalyst removed from saidalkylation reaction zone, and alkylate product recovered from saidreaction mixture, the improvement comprising diluting said hydrofluorlcacid contained in said reaction mixture at the end of said predeterminedreaction time to a concentration below its eective catalystconcentration by admixing water therewith in a mixing zone whereby theaikylation reaction is substantially instantaneously stopped.

4. ln a continuous alkylation process wherein an isoparamn, an olefin,and hydroiiuoric acid catalyst are maintained in intimate contact in analkylation reaction zone for a predetermined reaction time, reactionmixture of hydrocarbons and hydrofluoric acid catalyst removed from saidalkylation reaction zone, andalkylate product recovered from saidreaction mixture, the improvement comprising diluting said hydroiluorlcAacid contained in said reactionmixture at the end of said predeterminedreaction time to a concentration below its effective catalystconcentration by admixing dilute aqueous hydrouoric acid therewith in amixing zone whereby the alkylation reaction is substantiallyinstantaneously centration below its eiective vcatalyst concentration byadmixing dilute aqueous hydroiluoric acid therewith in a mixing zone,separating inactive hydrouoric acid from the resulting mixture,

separating at least a portion of said inactive hydrofiuoric acid into ahydrofluoric acid fraction of catalyst concentration and an aqueoushydrotluoric acid fraction below catalyst concentration, recycling saidhydrofiuoric acidv fraction of catalyst concentration to said alkyiationreaction zone, and recycling said aqueous hydroiluoric acid fractionbelow catalyst concentration to said mixingy zone.

6. In a continuous alkylationprocess wherein an isoparailin, an olenn,and hydrofluoric acid catalyst are maintained in intimate contact in` analkylation reaction zone for a predetermined reaction time, reactionmixture of hydrocarbons and hydroiuoric acid catalyst removed from saidalmlation reaction zone, and alkylate product recovered from saidreaction mixture, the improvei ment comprising diluting saidhydroiluoric acid contained in said reaction mixture at the end of saidpredetermined reaction time to a concentration below its eiectivecatalyst concentration by admixing dilute aqueous hydroiiuoric acidtherewith in a mixing zone, separating inactive hydrouoric acid from theresulting mixture, separating at least a portion of said inactivehydroiiuoric acid into a hydrciluoric acid fraction` of catalystconcentration and an aqueous hydroiluoric acid fraction below -catalystconcentration, recycling said hydrofiuoric acid fraction of catalystconcentration'to said alkylation reaction zone, cooling at least aportion of said aqueous hydrouoric acid fraction below catalystconcentration, and recycling said aqueous hydronuoric'acid fractionbelow catalyst concentration to said mixing zone.

7. A continuousalkylation process comprising contacting an isoparamn, anoleiin, and hydrouoric acid catalyst in an alkylation reaction zone fora predetermined reaction time, diluting the hydrouoric acid in thereaction mixture so.

formed with dilute aqueous hydronuoric acid to centration at the end ofsaid predetermined reaction time in a mixing zone, separating theresulting mixture into an aqueous hydrofluoric acid phase and ahydrocarbon phase, recovering alkylate product from said `hydrocarbonphase, separating at least a portion of said aqueous hydrouoric acidphase-into a hydroiluoric acid fraction of catalyst concentration and anaqueous hydroiluoric acid fractionbelow catalyst concentration,recycling said hydrouoric acid fraction of catalyst concentration tosaid alkylation reaction zone, cooling at least a portion of saidaqueous hydrouoric acid fraction below catalyst concentration, andrecycling said aqueous hydrofluorlc acid fraction below catalystconcentration to said mixing zone. Y

13. A continuous alkylation process comprising contacting anisoparaiiin, an olefin, and hydrofluoric acid catalyst in an alkylationreaction zone for a predetermined reaction time, diluting the hydrouorcacid inthe reaction mixture so formed with dilute aqueous hydrofluoricacid to a concentration below its eilective catalyst concentration attheend of said predetermined reaction time in a mixing zone, separating'the resulting mixture into an aqueous hydroiiuoric acid phase and ahydrocarbon phase, recovering alkylate product from said hydrocarbonphase, separating said aqueous hydrofluoric acid phase into 14. Acontinuous alkylationprccess comprising contacting an isoparaiiin, anolefin, and hydrofluoric acid catalyst in an alkyiation reaction 4,0zone for a predetermined reaction time, diluting a concentration belowits effective catalyst concentration at the end of said predeterminedreaction time in a mixing zone, separating the resulting mixture into anaqueous hydroiluoric acid phase and a hydrocarbon phase, recoveringalkylate product from said hydrocarbon phase, separating at 'least a-portion of saidv aqueous hydroiiuoric acid phase into a hydrofiuorioacid fraction of catalyst concentration and an aqueous .hydrotluoricacid fraction below catalyst concentration, recycling said hydroiluoricacid fraction ofl catalyst concentration to said alkylation re`- actionzone, and recycling said aqueous hydrothe hydrofluoric acid in thereaction 4mixture so' formed with dilute aqueous hydrouoric acid to aconcentration below its enective catalyst concentration at the end ofsaid predetermined reaction time in a mixing zone, separating theresulting mixture into an aqueous hydroiluorlc acid .phase and ahydrocarbon phase, recovering alkylate product from said hydrocarbonphase, recyclying a portion of said aqueous hydroiiuoric acid phase tosaid alkylation reaction zone, separating the remaining portion of saidaqueous hydrouoric acid phase into a hydrotluoric acid fraction ofcatalyst concentration and an aqueous hydrouoric acid fraction belowcatalyst concentration, recycling said hydroiiuorlc acid fraction -ofcatalyst concentration to said alwlation reaction zone, and recyclingsaid aqueous hydrofluoric acid fraction below catalyst concentrationiluorlc acid fraction below catalyst concentration to said mixing zone.

8. The process of claim 'l wherein the isoparafiin is isobutane and theolenn is a butene.

9. 'I'he process of -claim 7 wherein-the iso.- paraftin is isobutane andthe olenn is isobutene. 10. The process of claim 7 wherein the iso- Vparailln is isobutane and the olefin is butene-Z.

11, The process-of claim 'I wherein the`isoparamn is isobutane and theolen is propylene.

12. A continuous alleviation process comprising contacting an isoparamn,an oleiln, and hydroiluoric acid catalyst -in an alkylation reactionzone for a predetermined reaction time, diluting the hydrouoric acid inthe reaction mixture so formedl with dilute aqueous hydroiluoric acid-to to said mixing zone.

15. .il continuous alkylation process comprising contacting anisoparaiiln, an oien and hydrouoric acid catalyst in an alkylationreaction zone fora predetermined reaction time, diluting the hydrouoricacid in the reaction mixture so formed with -dilute aqueous hydrouoricacid to a concentration below its effective catalyst concentration attheend of said predetermined reaction time in a mixing zone, separatingthe resulting mixture into an aqueous hydroiiuoric acid ,n phase and ahydrocarbon phase, recovering al'- kylate product from said hydrocarbonphase, recycling a portion of said aqueous hydrouoric acid phase to said.mixing zone, separating the remaining portion of said aqueoushydrouorlc a concentration below its effective catalyst con-y 75 acidphase into a hydroiiuoric acid traction o! catalyst concentrationand anaqueous hydro-` uoric acid fraction below catalyst concentration,recycling said hydrouoric acid fraction of catalyst concentration tosaid alkylation reaction zone, and recycling said aqueous hydroiluoricacid fraction below catalyst concentration to said mixing zone.

16. A continuous alkvlation process comprising i contacting anisoparaiiin, an olen, and hydrouoric acid catalyst in an alkylationreaction zone for a predetermined reaction time, diluting thelu/droiiuoric acid in. the reactionmixture sc iormed with dilute aqueoushydrofiuoric acid to a concentration below its effective catalystconcentration at the end of said predetermined reaction time in a mixingzone, separating the resulting mixture into an aqueous hydrofluoric acidphase anda hydrocarbon phase, recovering a1- kylate product from saidhydrocarbon phase, recycling a portion of said aqueous hydroiluoric acidphase to said alkylation reaction zone, recycling another portion ofsaid aqueous hydrofluoric acid phase to said mixing zone, separating theremainder of said aqueous hydrofluori'c acid phase into a hydrouoricacid fraction of catalyst concentration and an aqueous hydrofluoric acidfraction below catalyst concentration, recycling said hydrofluorc acidfraction -of catalyst concentration to said alkylation reaction zone,and recycling said aqueous hydroiiuoric acid frajction below catalystconcentration to said mixing zone.

17. A continumxs alkylation process comprising contacting anisoparaflin, an olen, and hydroiluoric acid catalyst in an alkylationreaction zone for a predetermined reaction time, diluting thehydroiuoric acid catalyst in the reaction mixture so formed at the endof said predetermined reaction time to a concentration between 90 weightper cent of hydrouoric acid at a temperature of the reaction. mixture of10 C'. and '75 weight per cent of hydrouoric acid at a temperature ofthe reaction mixture of 50" C. by admixing therewith in a mixing zone asumcient quantity of aqueous hydrouoric acid having a concentration ofbetween about`36 and 65 weight per cent of hydroiuoric acid, separatingthe resulting mixture into an aqueous hydroiluoric acid phase and ahydrocarbon phase, recovering alkylate product from said hydrocarbonphase, separating .at least a portion f said aqueous hydrouoric acid'phase into a hydrouoric acid fraction of catalyst concentration and afraction having a hydrouoric acid concentration of between about 36 and65 weight per cent, recycling said fraction of catalyst concentration tosaid alkylation reaction zone, and recycling said fraction having a,hydroiiuoric acid concentration of between about 36 and 65 weight percent to said :mixing zone after cooling at least a. portion of saidfraction to a temperature between 16 C. and 0 C.

